Carb entries over maximum limit show an alert that cannot be dismissed #946

Describe the bug
Entering a carb size >250g creates an onscreen alert that cannot be closed. The only resolution is to force close the app.

Attach an Issue Report
Tap the Loop settings icon on the bottom of the screen, then tap Issue Report and attach it to this ticket.

To Reproduce
Steps to reproduce the behavior:

1. Click new carb entry
2. Enter a value >250g (2,356g for example)
3. Click save
4. See error

Expected behavior
An error appears that can be dismissed, so the input can be corrected.

Screenshots

Phone

• Hardware: iPhone XS
• OS Version: 12.2

Loop Version

• Version Number: 1.10.0
• Repo: LoopKit/Loop omnipod-testing branch

CGM

• Device: Dexcom G6
• Manager app: Dexcom App

Pump

• Manufacturer: Omnipod
• Model: Eros
• Firmware version: n/a

Additional context
Add any other context about the problem here.